The Whizlabs class and practice exams were good. I also studied with acloud.guru and the official Amazon study guide. If you want to pass this exam you need to repeatedly do all the labs you can find, all the practice exams you can find, and attempt to memorize every bit of tiny detail for architect, sysop, and developer you possibly can. There is no limit to the level of detail to which Amazon will go to get another test fee.